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Journal of Integrative Agriculture  2022, Vol. 21 Issue (3): 762-773    DOI: 10.1016/S2095-3119(21)63679-1
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Melanin, DNA replication, and autophagy affect appressorium development in Setosphaeria turcica by regulating glycerol accumulation and metabolism
GUO Xiao-yue*, LIU Ning*, LIU Bing-hui, ZHOU Li-hong, CAO Zhi-yan, HAN Jian-min, DONG Jin-gao
State Key Laboratory of North China Crop Improvement and Regulation/Key Laboratory of Hebei Province for Plant Physiology and Molecular Pathology/Mycotoxin and Molecular Plant Pathology Laboratory, Hebei Agricultural University, Baoding 071001, P.R.China
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玉米大斑病是世界玉米产区主要的真菌病害之一,引起该病害的真菌为玉米大斑病菌(Setosphaeria turcica),为异宗配合真菌,其无性态为玉米大斑凸脐孺孢(Exserohilum turcicum)。玉米大斑病菌分生孢子萌发后形成高度特化的侵染结构—黑化的附着胞。附着胞通过产生高膨压来穿透植物表皮,其中甘油是产生膨压的主要来源。本研究分析了附着胞侵染玉米叶片的位置,发现大多数萌发的分生孢子通过直接穿透表皮细胞进入叶片内部,无论是通过表皮细胞还是气孔侵染玉米叶片,附着胞都是侵染所必需的。为了进一步确定影响附着胞发育的关键因素,我们分析了黑色素抑制剂(三环唑,TCZ)、DNA复制抑制剂(羟基脲,HU)和自噬抑制剂(3-甲基腺嘌呤,3-MA)等对附着胞膨压和甘油含量的影响。结果表明,在对照和抑制剂处理下,附着胞膨压和甘油浓度在附着胞成熟阶段均达到最高水平,三种抑制剂在附着胞成熟阶段对附着胞膨压的影响最大,糖原和脂质体是产生甘油的主要物质。研究发现,在附着胞的发育过程中,抑制剂会影响糖原和脂质体在分生孢子、芽管和附着胞中的分布。黑色素、DNA复制和自噬通过调节甘油积累和代谢影响玉米大斑病菌附着胞的发育,该研究可为附着胞膨压和甘油含量之间的关系提供新的见解。

Abstract  Setosphaeria turcica (syn. Exserohilum turcicum) is the pathogenic fungus of maize (Zea mays) that causes northern leaf blight, which is a major maize disease worldwide.  Melanized appressoria are highly specialized infection structures formed by germinated conidia of S. turcica that infect maize leaves.  The appressorium penetrates the plant cuticle by generating turgor, and glycerol is known to be the main source of the turgor.  Here, the infection position penetrated by the appressorium on maize leaves was investigated, most of the germinated conidia entered the leaf interior by directly penetrating the epidermal cells, and the appressorium structure was necessary for the infection, whether it occurred through epidermal cells or stomata.  Then, to investigate the effects of key factors in the development of the appressorium, we studied the effects of three inhibitors, including a melanin inhibitor (tricyclazole, TCZ), a DNA replication inhibitor (hydroxyurea, HU), and an autophagy inhibitor (3-methyladenine, 3-MA), on appressorium turgor and glycerol content.  As results, appressorium turgor pressure and glycerol concentration in the appressorium reached their highest levels at the mature stage of the appressorium under the control and inhibitor treatments.  The three inhibitors had the greatest effects on appressorium turgor pressure at this stage.  Glycogen and liposomes are the main substances producing glycerol.  It was also found inhibitors affected the distribution of glycogen and liposomes, which were detected in the conidia, the germ tube, and the appressorium during appressorium development.  This study provides profound insight into the relationship between appressorium turgor pressure and glycerol content, which was affected by the synthesis of melanin, DNA replication, and autophagy in the developing appressorium during a S. turcica infection.  
Keywords:  Melanin        DNA replication        autophagy        appressorium        development        Setosphaeria turcica        glycerol  
Received: 06 January 2021   Accepted: 11 March 2021
Fund: This work was supported by the grants from the National Natural Science Foundation of China (32072370 and 31901827), the China Agriculture Research System of MOF and MARA (CARS-02-25), the Natural Science Foundation of Hebei Province, China (C2020204039 and C2018204059), and the Projects of Overseas Foundation, Hebei Province, China (C20190508). 
About author:  GUO Xiao-yue, E-mail:; Correspondence CAO Zhi-yan, Tel: +86-312-7528142, E-mail:; HAN Jian-min, Tel: +86-312-7528876, E-mail: * These authors contributed equally to this study.

Cite this article: 

GUO Xiao-yue, LIU Ning, LIU Bing-hui, ZHOU Li-hong, CAO Zhi-yan, HAN Jian-min, DONG Jin-gao . 2022. Melanin, DNA replication, and autophagy affect appressorium development in Setosphaeria turcica by regulating glycerol accumulation and metabolism. Journal of Integrative Agriculture, 21(3): 762-773.

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